This invention relates generally to solid compositions of biocidal compounds. In particular, this invention relates to solid compositions that provide controlled release of biocidal compounds.
The ability to control release of biocidal compounds to a locus to be protected is important in the field of biocidal compounds, especially in the field of microbicides and marine antifouling agents. Typically, when a biocidal compound is added to a locus to be protected, the compound is rapidly released, whether or not it is needed. Controlled release compositions deliver the biocidal compound in a manner that more closely matches the need for the compound. In this way, only the amount of the biocidal compound needed is released into the locus to be protected. Controlled release offers the advantages of reduced cost, lowered toxicity and increased efficiency.
Solid formulations of biocidal compounds are a useful method of delivering biocidal compounds to a locus to be protected. Solid formulations also offer the advantage of safening the biocidal compound by reducing the possibility of human exposure. For example, solid compositions eliminate the splash hazard that is common with liquid compositions.
Various solid compositions of biocidal compounds are known. Such methods include encapsulation of the biocidal compound, adsorption of the biocidal compound on an inert carrier, such as silica gel, and clathration of the biocidal compound.
However, such solid compositions do not always provide controlled release of the biocidal compounds. For example, solid compositions where the biocidal compound is adsorbed on an inert solid carrier usually do not control the release of the biocidal compound. Typically, once such a solid composition is added to a locus to be protected, the biocidal compound is rapidly released. Thus, any safening of the biocidal compound provided by the solid composition is lost once the composition is added to the locus.
For example, EP 106 563 A (Melamed) discloses microbicidal compositions having a water soluble microbicide admixed with an inert, finely-divided, water-insoluble solid carrier, such as clays, inorganic silicates and silicas. These compositions do not provide controlled release of the biocidal compounds. The compounds release into the locus by dissolution, and therefore, their release is controlled by the dissolution rate of the particular biocidal compound. This application does not disclose zirconium hydroxide.
Hydroxides of certain metals, such as zirconium, titanium, iron, vanadium and tin, have been disclosed to chelate antibiotics (Kennedy et al. Antimicrob. Agents Chemother., 9, 766-770 (1976)). The focus of this paper is on antibiotic immobilization. Although Kennedy et al. disclose that the metal hydroxides tested may slowly release antibiotics, Kennedy et al. do not recognize the special ability of zirconium hydroxide to control the release of biocidal compounds. The other metal hydroxides in Kennedy et al., such as titanium hydroxide, do not control the release of biocidal compounds. There is no discussion of microbicidal compounds or marine antifouling agents.
The problem addressed by the present invention is to provide solid compositions of biocidal compounds that are safer to handle and provide controlled release of biocidal compounds once the composition is added to a locus to be protected.